Perhaps I can add to it, (By pocking @Sigma with a completely Scifi technology proposal.)

How theoretically plausible would be the use of the Sonoluminescent Effect to pump water with light as a Stimulated Emmision medium? You know, to make "some kind of audio-vibratory physio-molecular transport device?" ~Scottie. (No, not that one, this one:)

_________________"You can't have everything, where would you put it?" -Steven Wright.

Actually, what I had in mind was for the laser to steamify the liquid water inside the rocket, and the steam going out the bottom would equal force and opposite direction the thing upwards. So the laser wouldn't have to touch the rocket, only the water. Anyway, just an idea.

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

Actually, what I had in mind was for the laser to steamify the liquid water inside the rocket, and the steam going out the bottom would equal force and opposite direction the thing upwards. So the laser wouldn't have to touch the rocket, only the water. Anyway, just an idea.

Got that, and I'm not saying it won't work, but helping you out with the technical challenges involved. First of all, the rocket is moving, and if you've ever flown in anything I don't have to tell you the atmosphere is not smoth, and uniform. Meanwhile, you're keeping a Laser uniform, and on target to steamify said water. That means there's a good chance that some of the directed energy is likely to hit some part of the craft at some point, unless you luck out with the most perfect space launch in recorded history. Hope for the best, but design for the worst case scenario, Space Flight isn't the safest way to go, what with all the energies involved, and near instadeath right outside your window the whole way up. Anything goes wrong, and it's most likely to be catastrophic. Alls I'm sayin'.

_________________"You can't have everything, where would you put it?" -Steven Wright.

I think using your laser on the front of the craft makes more sense, and have it all bloom into plasma, and then push that plasma back,

intresting fact, plasma can be charged with radio.....

a directed H.e.r.f system could deliver IMMENSE amounts of power,

so you use on board laser, to make "plasma column" and then throw that through the center of the ship, and some how get power induced in it out....

So, you're going to throw massive amounts of energy forward, expand air in front of the ship, and then take it inside when it's already expanded? There's really no net gain from that. Intake the air through simple ram effect to compress it, heat it internally with your laser, radio field effect, or whatever, and let it expand out the back. This is how thrust works. What you're talking about is a massive waste of energy.

_________________"You can't have everything, where would you put it?" -Steven Wright.

When you heat air, it expands, and goes up. Without taking the craft with it. This is the principle that a hot air balloon works on, but only with a canopy to contain it. Without that critical part, it will just dissipate, and your craft goes nowhere. I made a scale model using a similar principle with a Cryo-convection annular (Ring shaped) surface. It floated, but never broke Surface effect, because apparently it needed the ground to push against, and it wouldn't scale up. This is because of the Square/cube law, if you double the size of a plane, for instance, you have 4 times the wing surface, but 8 times the mass. And that was with a principal where the energy vector was going in the right direction. It would have made a safe hovercraft, but the energies to make it work were far too high.

What you just proposed would work with a freeze ray, to compress a column air, and let it sink through the craft, if there was anything like a freeze ray outside of comic books. Heating it above the craft will get you nowhere, and even if it did work, it won't get you to space, because you'll run out of air eventually, and there's no where to put a rocket upper stage. No way that will work, ever unless the laws of convection were somehow reversed.

_________________"You can't have everything, where would you put it?" -Steven Wright.

Actually, what I had in mind was for the laser to steamify the liquid water inside the rocket, and the steam going out the bottom would equal force and opposite direction the thing upwards. So the laser wouldn't have to touch the rocket, only the water. Anyway, just an idea.

Got that, and I'm not saying it won't work, but helping you out with the technical challenges involved. First of all, the rocket is moving, and if you've ever flown in anything I don't have to tell you the atmosphere is not smoth, and uniform. Meanwhile, you're keeping a Laser uniform, and on target to steamify said water. That means there's a good chance that some of the directed energy is likely to hit some part of the craft at some point, unless you luck out with the most perfect space launch in recorded history. Hope for the best, but design for the worst case scenario, Space Flight isn't the safest way to go, what with all the energies involved, and near instadeath right outside your window the whole way up. Anything goes wrong, and it's most likely to be catastrophic. Alls I'm sayin'.

Mortars are pretty darn small, and there are laser systems that can hit them, as they are moving. So are kassam rockets, by the way. And they both are a lot smaller than the business end of a full sized rocket engine. Of course, they fly a lot lower. But if you are going to use a water rocket, I think that is the way to go. Also, it may be possible to design the rocket like bell bottom pants, or like a blunderbuss, or like, um, a bell . . . well, you get the idea. The point is that if the bottom of the rocket is covered with water (or steam), there isn't so much of a danger of the laser missing and hitting the rocket. But of course, doing it as it is done now is probably more efficient and cheaper.

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

Mortars are pretty darn small, and there are laser systems that can hit them, as they are moving. So are kassam rockets, by the way. And they both are a lot smaller than the business end of a full sized rocket engine. Of course, they fly a lot lower. But if you are going to use a water rocket, I think that is the way to go. Also, it may be possible to design the rocket like bell bottom pants, or like a blunderbuss, or like, um, a bell . . . well, you get the idea. The point is that if the bottom of the rocket is covered with water (or steam), there isn't so much of a danger of the laser missing and hitting the rocket. But of course, doing it as it is done now is probably more efficient and cheaper.

Right, but with a Mortar round, the idea is to destroy it. Good job designing around the problems I brought up, but how do you plan to keep the water in an open base bell shape?

_________________"You can't have everything, where would you put it?" -Steven Wright.

Mortars are pretty darn small, and there are laser systems that can hit them, as they are moving. So are kassam rockets, by the way. And they both are a lot smaller than the business end of a full sized rocket engine. Of course, they fly a lot lower. But if you are going to use a water rocket, I think that is the way to go. Also, it may be possible to design the rocket like bell bottom pants, or like a blunderbuss, or like, um, a bell . . . well, you get the idea. The point is that if the bottom of the rocket is covered with water (or steam), there isn't so much of a danger of the laser missing and hitting the rocket. But of course, doing it as it is done now is probably more efficient and cheaper.

Right, but with a Mortar round, the idea is to destroy it. Good job designing around the problems I brought up, but how do you plan to keep the water in an open base bell shape?

Well, you squirt water down the sides of the bell, and it adheres by hydrogen bond, or simply by pressure. That's just for cooling. The thrust you get by the laser hitting up the middle. This is fun!

_________________“Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return.” -Anonymous

It seems you guys haven't seen or heard about this. Of course if you use propellant to squirt into the chamber at the bottom, you could do without air.

My guess about why LaserMotive would go for shooting laser at a heatexchanger and then basically using normal rocketry for the craft is that we already have that technology.

We have powerful enough lasers, we have good enough optics to aim said lasers, we have the heatexchanger technology as far as that study I posted can be trusted.

The only issue is as usual is sufficient investment to actually demonstrate that this can actually fly.

Of course we are still talking a couple of billion dollars to build the system to launch 100kg payloads, and certainly it would require high demand for this system to pay off, but the advantage of low chance of critical failure /because of the redundancy of using hundreds or thousands of lasers/, and the ease of scalability of this system probably makes it worth it.

If you want to launch bigger payloads, you just increase the size of your craft and increase the power of your lasers, or increase their number /or both/. And you can do all that while your system is running because you can just take lasers offline and upgrade them one by one, or just add more to the grid around the edges etc...

Also you can upgrade your crafts by increasing their operational temperatures, and maybe at some point you can do what they propose in the video above where you generate plasmas with your laser or beamed microwaves to generate thrust, but before then heating gasses to be used in normal rocket engines seems like a good stepping stone.

Also the lasers you would develop for this could be used in space for interplanetary travel or transportation using ablative surfaces, or energy beaming over large distances.

I had seen that design, but not that vignette on it. Again, anything that depends on the ambient air won't reliably get you to space, because you eventually run out of air. The first 5 minutes is an experimental prototype. The last part is Science Fiction losely based on several different proposals that never even got funded by NASA, plus a classic Flying Saucer because people who watch Discovery think in terms of Flying Saucers.

_________________"You can't have everything, where would you put it?" -Steven Wright.

I had seen that design, but not that vignette on it. Again, anything that depends on the ambient air won't reliably get you to space, because you eventually run out of air. The first 5 minutes is an experimental prototype. The last part is Science Fiction losely based on several different proposals that never even got funded by NASA, plus a classic Flying Saucer because people who watch Discovery think in terms of Flying Saucers.

It was just a video I could quickly find with the design in it. I ignored the last bit too.

The point of posting that video to illustrate what supershuki was talking about and show it has already been demonstrated to work on small scale, although it didn't use onboard fuel.

But if you replace the atmosphere with an onboard tank of a suitable reaction mass, you can use this outside the atmosphere as long as you can focus a laser light onto the mirror/rocket engine.

The issue is of course is that when you are in space, you want to thrust horizontally to raise or lower your orbit, and with the powersource on the ground, aiming the laser into the where the propellant should come out becomes tricky.

Easy solution is to use a heatexchanger on the bottom of the craft, onboard hydrogen or water in a tank, and just heat the reaction mass that way. You might not get as high isp as what you would if you generated a plasma, but you still get high enough to get to orbit in one stage.

Also this all depends on the scale, if you scale your array, and powerbeaming up, you could in theory use beamed energy to create plasma use that as your exhaust and increase the efficiency of your rocket later on. But the key is you don't have to start that complex. You can start with plain old hot gasses coming out the back.

Seeing how we probably won't get to fly compact nuclear powerplants to orbit anytime soon, beaming the power from the ground seems to be the next best thing for scaling up the amount of material we can launch while reducing costs.

At the moment we are flying a whole extremely not compact chemical powerplant with every rocket we launch. If we don't launch the plant with the rocket, we save a whole truckload of fuel and energy. Although we should do the math.

Use a solar array to split water for rocket fuel, then use the fuel in a rocket to get to orbit. Calculate how much energy was needed for 1kg to get to orbit starting at the solar powerplant collecting it, ending with the 1kg's kinetic and gravitational potential energy in LEO.

Then use the same array to power lasers to heat the reactionmass on a rocket we are discussing here. Calculate how much energy was needed for 1kg to get to the same orbit.

The winner should be the approach we take seeing how we want to get off of fossil fuels, yet still would like to expand into space and beyond, without touching anything "nuclear".

Out of all the proposals out there like launch loops, or space elevators, beamed power seems to be the easiest to achieve with our current technology and economy. It could potentially be even cheaper than vertically landing all stages of a multistage rocket. Although if you add the two technology, and you land and reuse your laser rocket, you got it all made.

I am not sure where airbreathing hybrid rockets like skylon fit into this picture, but I do wonder if beamed power could work with them too.

The point of posting that video to illustrate what supershuki was talking about and show it has already been demonstrated to work on small scale, although it didn't use onboard fuel.

That model is hollow, and I believe made from aluminum. Scroll up for an explanation of the Square/Cube law concerning scaling, only instead of a Plane, insert the collection surface, then add a payload...

Quote:

But if you replace the atmosphere with an onboard tank of a suitable reaction mass, you can use this outside the atmosphere as long as you can focus a laser light onto the mirror/rocket engine.

The issue is of course is that when you are in space, you want to thrust horizontally to raise or lower your orbit, and with the powersource on the ground, aiming the laser into the where the propellant should come out becomes tricky.

Or, use the ground based LASER to get up to altitude on atmospheric effect, then transit to an orbital Laser to react the onboard mass by squirting water onto the illuminated surface. I like the "Bell" shape more than the negative ogive curve from the video, because it contains the expansion rather than dissipating it outwards as a loss vector. (It would theoretically be more efficient.)

Quote:

You might not get as high isp as what you would if you generated a plasma, but you still get high enough to get to orbit in one stage.

Also this all depends on the scale, if you scale your array, and powerbeaming up, you could in theory use beamed energy to create plasma use that as your exhaust and increase the efficiency of your rocket later on. But the key is you don't have to start that complex. You can start with plain old hot gasses coming out the back.

I am not sure where airbreathing hybrid rockets like skylon fit into this picture, but I do wonder if beamed power could work with them too.

The example from the video is basically "Air Breathing" in that the Reaction Mass is ambient, and will probably fall off with altitude. Single Stage has the challenge that the conditions change from external pressure to relative vacuum, so you're forced to chose between an engine that works halfway decent in both conditions (Like an Aerospike) multiple engines for each stage, or theoretically one that changes in transit to adapt with the changing conditions.

The latter would be ideal, if we could work out making a flexible nozzle that alters it's curvature from a deep parabola at sea level to a shallow dish in relative vacuum. (An early proposal was an annular parabola that dropped ring sections from the edge in stages so you could stage with 1 nozzle.) Also, I'd think some modification of Reaction mass mixture could get higher efficiency throughout the launch envelope, since you want a dense fuel (Like Mercury if pollution wasn't an issue) in heavy atmosphere, and a light one like Hydrogen at relativistic speeds in orbit.

_________________"You can't have everything, where would you put it?" -Steven Wright.